The present invention relates generally to a superconductive coil in a synchronous rotating machine. More particularly, the present invention relates to an apparatus and method for manufacturing superconducting field windings in the rotor of a synchronous machine.
Synchronous electrical machines having field coil windings include, but are not limited to, rotary generators, rotary motors, and linear motors. These machines generally comprise a stator and rotor that are electromagnetically coupled. The rotor may include a multi-pole rotor core and coil windings mounted on the rotor core. The rotor cores may include a magnetically-permeable solid material, such as an iron-core rotor.
Conventional copper windings are commonly used in the rotors of synchronous electrical machines. Electrical resistance of copper windings, however, is sufficient (although low by conventional measures) to contribute to substantial heating of the rotor and to diminish the power efficiency of the machine. Recently, superconducting coil windings have been developed for rotors, which have effectively no resistance and are highly advantageous rotor coil windings.
High temperature superconducting coils used as the rotor field windings of the electrical machine must be designed as rigid structures made with precise dimensional tolerances so that the structural support can fit to the coil without excessive clearances that may result in high strain and potential damage to the coil during loading. The spring back of the tape conductor as it is wound on the straight sections of a racetrack coil form results in poor packing factor and lower strength of the composite compared to the circular sections.
Typical superconductor rotor windings are made from saddle-shaped coils that are assembled around cylindrical shells for structural support. These saddle-shaped coils are complex winding structures that may result in overstraining the high temperature superconducting (HTS) tape conductor by the winding operation as a result of tight bend diameters, twisting of leads, and differential thermal strain of the winding relative to the support structure during cool down.